// 对象扩展方法 Object.assign

const source1 = {
    a: 123,
    b: 123
}
const source2 = {
    b: 789,
    d: 789
}
const target = {
    a: 456,
    c: 456
}

const result = Object.assign(target, source1, source2)

console.log(target)
console.log(result === target)
